A large-scale review of genetic data from a number of different studies has suggested that diverse parental genes can lead to offspring who are taller and have increased cognitive ability.
Dr Nathan Richardson, head of molecular and cellular medicine at the UK's Medical Research Council, which funded the research, said: 'Most people would believe a diverse gene pool is a good thing, but the discovery that height is associated with diversity wouldn't have been foreseen.'
It has long been known that children born of two closely related parents have increased incidences of genetic diseases because they are more likely to inherit the same harmful gene variants from both parents.
However, few studies have examined the potential positive effects of breeding between more distantly related individuals. To investigate this theory the researchers analysed 110 separate genome studies involving over 350,000 participants across four continents.
To measure how closely related a person's parents are the researchers measured the instances of two identical copies of specific genes — one from the mother and one from the father. This genomic data is much more reliable than using family trees or pedigrees.
The researchers then compared the degree of parental genetic diversity against 16 health traits and looked for correlations. Only four of these traits — height, lung capacity, cognitive ability and educational attainment — increased in line with the degree of parental diversity.
The researchers calculated that, on average, the offspring of first cousins are 1.2 centimetres shorter and have 10 months less formal education than the children of more genetically diverse parents.
Dr Peter Joshi of the University of Edinburgh's Centre for Population Health Sciences and co-author on the paper said: 'We've found that the genetics are associated quite robustly across populations and, although we tried to compensate for environmental factors, we think the genetic effects are real.'
Contrary to previous studies, no link was found between parental diversity and cholesterol levels, blood pressure or the incidence of diabetes.
In modern society it is common for someone's parents to come from distant parts of the world, which means that we have an increasingly diverse gene pool. The findings of this study support the idea that increased height and cognitive ability have been positively selected for over many generations.
Study co-author Dr Jim Wilson said: 'This study highlights the power of large-scale analyses to uncover fundamental information about our evolutionary history.'
The study was published in Nature.